1. Field of the Invention
The invention relates to an apparatus for developing sheet- or strip-type photographic material.
2. State of the Art
Apparatuses for developing sheet- or strip-type photographic material are widely known in the photo finishing field, being known as film processors in the case of films to be developed and paper processors in the case of exposed paper. Especially in the case of paper processors, it can happen that the paper exposed in the printer and to be developed in the paper processor is either in single-sheet form or in the form of long strips of paper, which are not cut apart into individual paper pictures until after development. The single sheets or paper strips are transported for developing through one or more wet chemical baths, and the development of the pictures takes place by the action of the developer fluid.
The volume of such wet-chemical baths in the processors--for the sake of simplicity, only paper processors will be discussed hereinafter--depends substantially on what throughput (number of developed pictures per unit of time) the particular user, as a rule developing labs, seeks to attain. For a relatively high throughput, the distance through the paper processor must be correspondingly long, so that there can be as many pictures as possible in the paper processor simultaneously, and with continuous transport on the one hand and a relatively fast transport speed on the other, the transit time of the paper through the paper processor matches the length of time necessary for the development (which of course is known beforehand). The consequence is baths of relatively large volume.
For the user of so-called minilabs or microlabs (both will hereinafter be referred to as minilabs). conversely, a substantially lower throughput is of interest. Accordingly, the transport speed through the wet-chemical baths can also be reduced. Only considerably smaller volumes are therefore required for the baths of such minilabs. However, for the baths of such minilabs it is also necessary that the developer fluid always be "fresh", so that the developed paper pictures will all meet a uniform standard of quality. As a consequence, the small-volume baths especially must be replaced or replenished from time to time. Moreover, lively motion of the wet-chemical baths in the paper processor has proven to be advantageous, since in this way fresh developer fluid is brought again and again into contact with the paper to be developed. It will be appreciated that complete replacement or replenishment of the baths occurs at shorter time intervals in smaller-volume baths than in larger-volume baths. Paper processors with small-volume baths have therefore already been proposed, for example, in U.S. Pat. Nos.: 5,179,404; 5,309,191; 5,311,235; and 5,270,762.
After a certain length of time, however, the developer fluid in the paper processor becomes unusable (the developer fluid oxidizes), even if it has been virtually unused (for instance, if no developing jobs have been performed); it must then be completely replaced. The developer fluid must be replenished or regenerated so that it remains stable and does not become unusable. To this end, based on a per unit area of developed paper, a predetermined amount of regenerated or of fresh developer fluid must be added to the bath. The smaller the entire volume of developer fluid in the paper processor, the faster is practically all the volume of developer fluid located in the paper processor regenerated or replaced, even if the throughput is low. Paper processors which, in proportion to the throughput, furnish a small volume of developer fluid have therefore greater long-term stability.
Paper processors with high long-term stability are especially advantageous for the minilabs and microlabs already mentioned, in which the average throughput is relatively slight, yet which nevertheless needs high performance equipment to handle peak loads (as in one-hour photo developing). In such a minilab or microlab, the distance through the paper processor must therefore on the one hand be long enough to enable handling of the peak loads, while on the other hand, the entire volume of developer fluid must be as small as possible, so that high long-term stability is assured even at a low average throughput. The situation is similar on the professional level, where large paper sizes (poster size) require a large paper processor whose average throughput is nevertheless low.
Aside from the replacement or replenishment of the developer fluid, in paper processors the transport rollers (and as needed other elements of the paper processor) must also be cleaned from time to time, so that soiling of elements of the paper processor will not cause losses of quality in the developed paper pictures. This necessitates a complete interruption of the wet chemical developing processor. For cleaning, the rollers must either be removed from the paper processor, or they must be cleaned while remaining inside the paper processor--but as a rule, they are taken out for cleaning. For the most efficient possible use of the paper processor (and naturally this also applies to film processors), it is therefore desirable, and an object of the invention, that this cleaning be performed as simply and as fast as possible. In addition, the processor should be simple to manufacture and should be reliable in function.